全文获取类型
收费全文 | 1435篇 |
免费 | 101篇 |
国内免费 | 1篇 |
专业分类
林业 | 78篇 |
农学 | 34篇 |
基础科学 | 4篇 |
226篇 | |
综合类 | 228篇 |
农作物 | 63篇 |
水产渔业 | 124篇 |
畜牧兽医 | 656篇 |
园艺 | 28篇 |
植物保护 | 96篇 |
出版年
2023年 | 22篇 |
2022年 | 22篇 |
2021年 | 32篇 |
2020年 | 46篇 |
2019年 | 42篇 |
2018年 | 41篇 |
2017年 | 31篇 |
2016年 | 37篇 |
2015年 | 31篇 |
2014年 | 28篇 |
2013年 | 59篇 |
2012年 | 92篇 |
2011年 | 105篇 |
2010年 | 47篇 |
2009年 | 45篇 |
2008年 | 90篇 |
2007年 | 108篇 |
2006年 | 71篇 |
2005年 | 93篇 |
2004年 | 83篇 |
2003年 | 70篇 |
2002年 | 91篇 |
2001年 | 24篇 |
2000年 | 11篇 |
1998年 | 19篇 |
1997年 | 11篇 |
1996年 | 18篇 |
1995年 | 13篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 7篇 |
1991年 | 16篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 4篇 |
1979年 | 10篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 5篇 |
1971年 | 3篇 |
1967年 | 3篇 |
1966年 | 2篇 |
1931年 | 3篇 |
排序方式: 共有1537条查询结果,搜索用时 15 毫秒
61.
Aleš Lebeda Michaela Sedlářová James Lynn David A. C. Pink 《European journal of plant pathology / European Foundation for Plant Pathology》2006,115(4):431-441
Phenotypic and histological responses of cultivated lettuce (Lactuca sativa) and wild relatives L. saligna, L.␣virosa as well as interspecific crosses derived from L. sativa × L. serriola to two races of Bremia lactucae (CS2, CS9) were investigated. With the exception of L. sativa genotypes, all accessions and hybrids expressed incomplete or complete resistance to both pathogen races, with slight differences at seedling and adult plant stages, respectively. Histological features of the interactions (development of pathogen infection structures and host hypersensitive response to attempted infection) were studied on leaf discs 48 h after inoculation. Interactions with similar phenotypic expression of resistance were characterized by significant variation in rate of development of pathogen infection structures and hypersensitive reactions. Differences found within eight Lactuca spp. accessions and hybrids challenged by two distinct pathogen races are interpreted and discussed. 相似文献
62.
James E. Childs Laura E. Robinson Ramses Sadek Anthony Madden Mary Elizabeth Miranda Noel L. Miranda 《Preventive veterinary medicine》1998,33(1-4):207-218
We estimated the population density of dogs by distance sampling and assessed the potential utility of two marking methods for capture-mark-recapture applications following a mass canine rabies-vaccination campaign in Sorsogon Province, the Republic of the Philippines. Thirty villages selected to assess vaccine coverage and for dog surveys were visited 1 to 11 days after the vaccinating team. Measurements of the distance of dogs or groups of dogs from transect lines were obtained in 1088 instances (N = 1278 dogs; mean group SIZE = 1.2). Various functions modelling the probability of detection were fitted to a truncated distribution of distances of dogs from transect lines. A hazard rate model provided the best fit and an overall estimate of dog-population density of 468/km2 (95% confidence interval, 359 to 611). At vaccination, most dogs were marked with either a paint stick or a black plastic collar. Overall, 34.8% of 2167 and 28.5% of 2115 dogs could be accurately identified as wearing a collar or showing a paint mark; 49.1% of the dogs had either mark. Increasing time interval between vaccination-team visit and dog survey and increasing distance from transect line were inversely associated with the probability of observing a paint mark. Probability of observing a collar was positively associated with increasing estimated density of the dog population in a given village and with animals not associated with a house. The data indicate that distance sampling is a relatively simple and adaptable method for estimating dog-population density and is not prone to problems associated with meeting some model assumptions inherent to mark-recapture estimators. 相似文献
63.
Deborah S. Greco Rod A.W. Rosychuk Gregory K. Ogilvie Lynn M. Harpold Camilla H. Van Liew 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1998,12(1):7-10
Thirty adult, client-owned dogs were diagnosed with hypothyroidism based on history, physical examination findings, hematologic and biochemical abnormalities, thyrotropin (TSH) response testing, endogenous canine thyrotropin (cTSH) concentration, or both, and total serum thryoxine concentration. All dogs received levothyroxine (L-thyroxine) at an initial dose of 22 μg/kg PO sid in either a tablet (13 dogs) or chewable form (17 dogs). Energy expenditure of each dog during apparent rest was estimated with an open-flow indirect calorimetry system by determining the rates of carbon dioxide production and oxygen consumption. Energy expenditure of apparent rest (EE) was lower in untreated hypothyroid dogs compared with reference values for EE. After treatment with L-thyroxine, EE of the hypothyroid dogs was significantly ( P < .05) higher than pretreatment values. 相似文献
64.
Peter J. Ihrke Anthony A. Stannard Alex A. Ardans Sharon G. Yaskulski 《Veterinary immunology and immunopathology》1985,9(2):161-170
Skin biopsy specimens from 7 dogs with immune-mediated skin diseases diagnosed by routine histology and 5 dogs with other skin diseases were placed in Michel's transport medium for 4 to 9 years. Direct immunofluorescence yielded positive results in tissue samples from 3 dogs with pemphigus foliaceus and 2 dogs with discoid lupus erythematosus. Direct immunofluorescence was not seen in tissue samples from 1 dog with pemphigus foliaceus and 5 dogs with non immune-mediated skin diseases. Direct immunofluorescence was seen in skin biopsy specimens maintained in Michel's medium for 4 to 8 years. 相似文献
65.
66.
Summary A simple model, based on the use of transformations of second-order tensors, is presented in this paper to predict the failure
mode of wood members stressed in various degrees of parallel-and perpendicular-to-grain tension and parallel-to-grain shear.
This type of loading is indicative of structural wood members with cross grain or grain deviations in the vicinity of knots
subjected to bending or tension. The model is based on the assumptions that failure is dictated by the presence of any of
the aforementioned stresses that exceed the clear wood strength in that mode and that failure does not result from stress
interactions. The magnitudes of the applied stresses are normalized relative to the wood strength in that mode. The ratio
of applied stress to material strength that is greatest at any particular angle of load to grain is presumed to be the failure
mode at that angle. To verify model predictions, optical and microscopic analyses of surfaces of failed specimens loaded in
uniaxial tension at angles between 0° and 90° to grain were compared to previously obtained, or otherwise known, surfaces
of specimens tested in tension and shear. Specimens tested at various angles to grain demonstrated failed surfaces very much
like those associated with specimens loaded in the modes predicted by the model. 相似文献
67.
Guillermo Cabrera Walsh Anthony S. Dimeglio Ashot Khrimian Donald C. Weber 《Journal of pest science》2016,89(1):21-29
Harlequin bug (Murgantia histrionica) is an important pest of cole crops in the USA. The adults and nymphs feed on aboveground plant tissues by sucking cell contents and can seriously damage the host. Current insect control measures on cole crops target mainly lepidopteran pests, and the insecticides generally used do not control harlequin bug, so alternative management practices need to be explored. Previous research has established the existence of a male-produced pheromone attractive to both sexes and nymphs of M. histrionica. In this work, two systems of marking bugs were tested to verify if the mark affected fitness traits such as survival and host location. In a second phase, marked individuals were placed on trap host plants baited with synthetic pheromone lures to test whether migration rates were related to M. histrionica density on the trap plants and the presence of the attractants. Neither marking system affected the survival or orientation of the subjects compared to unmarked individuals. The pheromone lures significantly increased the attractiveness of the trap plants, but did not increase the retention time of the plants compared to unbaited plants. Emigration from the trap plants showed a constant rate and seemed unrelated to bug density on the plants. However, a mean peak density of ca. 36 bugs/plant was calculated. Beyond this number, density tended to decrease. These successful marking methods and retention time models support development of M. histrionica management with trap crops, by providing tentative control thresholds and decision rules. 相似文献
68.
The aqueous extract of Calotropis procera was evaluated for its spasmolytic effect using in vitro trachea smooth muscle chain of Guinea-pig. The extract (50, 100 and 200 microg/ml) showed a dose-dependent relaxant activity probably exhibited through the direct relaxant action on the smooth muscle. 相似文献
69.
Anthony S. Davis Douglass F. Jacobs Kevyn E. Wightman Zonda K. D. Birge 《New Forests》2006,31(2):293-303
Bareroot hardwood seedling production involves intensive soil management. To increase soil organic matter (OM), nurseries
commonly grow a cover crop for 1 year after every 1–2 year of seedling production. Raising soil OM levels can also be achieved
through addition of soil amendments. We studied the influence of chicken manure (CM) and composted leaf, tree, and lawn trimmings
(Cp) on soil properties and morphology of green ash (Fraxinus pennsylvanica Marsh.) and northern red oak (Quercus rubra L.) seedlings. CM was applied at 725, 1450, or 2900 kg ha−1 (CM725, CM1450, and CM2900, respectively) and Cp was applied at 200 m3 ha−1. Addition of CM and Cp significantly raised soil OM levels and altered soil chemical properties compared to the control (Ctrl).
Root-collar diameter increased with addition of CM1450, CM2900, or Cp compared to CM725 or Ctrl plots for northern red oak,
but was largest in soils amended with CM2900 for green ash. Conversely, height was greatest with addition of CM725 for northern
red oak, but green ash seedlings were shorter in Ctrl plots than in all amendments except for CM725. Root volume of green
ash and northern red oak seedlings was positively influenced by addition of CM or Cp. Seedling responses to nursery soil amendments
vary with different forms and amounts of OM. Benefits to seedling growth through application of appropriate materials in the
proper balance can improve seedling morphological quality and positively influence soil chemical properties. 相似文献
70.
Jessica Fry Juan Pérez Casanova Lynn Lush Andy Walsh Cyr Couturier 《Journal of aquatic animal health》2015,27(1):57-64
The direct exposure of fish eggs to ozonated water has generated interest as a means of ensuring pathogen-free eggs without the use of harsh chemicals. However, there are numerous knowledge gaps, including safe contact times, exposure levels, and potential long-term effects on aquaculture species in both freshwater and seawater. The effect of different ozone (O3) doses (0.5–1.0, 1.5–2.0, and 2.5–3.0 mg of O3/L for 90 s) on recently fertilized eggs of Atlantic Cod Gadus morhua and eyed eggs of Atlantic Salmon Salmo salar and Rainbow Trout Oncorhynchus mykiss was evaluated in comparison with the effects of two commercial disinfectants: Perosan (0.004 mg/L) and Ovadine (100 mg/L). The impact of ozone application was evaluated based on hatching success, larval nucleic acid concentration, larval growth, and survival. Overall, results indicated that ozonation of Atlantic Cod eggs at a dose less than 3.0 mg/L for 90 s produced no negative effect on the larvae up to 30 d posthatch. Furthermore, ozonation of Atlantic Salmon and Rainbow Trout eggs generated no negative effect on the larvae, based on monitoring until 85% yolk sac re-absorption (16 d posthatch).
Received May 6, 2014; accepted October 24, 2014 相似文献